U.S. patent number 11,164,687 [Application Number 17/052,684] was granted by the patent office on 2021-11-02 for shunt resistor mount structure.
This patent grant is currently assigned to KOA CORPORATION. The grantee listed for this patent is KOA CORPORATION. Invention is credited to Tamotsu Endo.
United States Patent |
11,164,687 |
Endo |
November 2, 2021 |
Shunt resistor mount structure
Abstract
Provided is a shunt resistor mount structure comprising: a shunt
resistor including a pair of electrodes and a resistive body; a
current detecting substrate having a control circuit mounted
thereon, the substrate having a voltage detecting portion to which
a pair of voltage detection terminals of the shunt resistor are
connected; and a temperature sensor for measuring a temperature of
the electrodes.
Inventors: |
Endo; Tamotsu (Nagano,
JP) |
Applicant: |
Name |
City |
State |
Country |
Type |
KOA CORPORATION |
Ina |
N/A |
JP |
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Assignee: |
KOA CORPORATION (Nagano,
JP)
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Family
ID: |
68539775 |
Appl.
No.: |
17/052,684 |
Filed: |
May 8, 2019 |
PCT
Filed: |
May 08, 2019 |
PCT No.: |
PCT/JP2019/018361 |
371(c)(1),(2),(4) Date: |
November 03, 2020 |
PCT
Pub. No.: |
WO2019/220964 |
PCT
Pub. Date: |
November 21, 2019 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20210158997 A1 |
May 27, 2021 |
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Foreign Application Priority Data
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May 17, 2018 [JP] |
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JP2018-095426 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H01C
1/14 (20130101); H01C 1/01 (20130101); G01K
7/183 (20130101); H01C 13/00 (20130101); H01C
13/02 (20130101) |
Current International
Class: |
H01C
1/01 (20060101); H01C 1/14 (20060101); H01C
13/00 (20060101); G01K 7/18 (20060101) |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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1030185 |
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Aug 2000 |
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EP |
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2000-500231 |
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Jan 2000 |
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JP |
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2003-270274 |
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Sep 2003 |
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JP |
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2013-174555 |
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Sep 2013 |
|
JP |
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Other References
English Translation of International Search Report from Application
No. PCT/JP2019/018361, dated Aug. 6, 2019, 2 pages. cited by
applicant .
Written Opinion, PCT/ISA/237, from Application No.
PCT/JP2019/018361, dated Aug. 6, 2019, 3 pages. cited by
applicant.
|
Primary Examiner: Lee; Kyung S
Attorney, Agent or Firm: Crowell & Moring LLP
Claims
The invention claimed is:
1. A shunt resistor mount structure comprising: a shunt resistor
including a pair of electrodes and a resistive body arranged
between the pair of electrodes in a longitudinal direction, wherein
the resistive body has a higher resistivity than the pair of
electrodes; a pair of voltage detection terminals provided,
respectively, on the pair of electrodes adjacent to the resistive
body, wherein each voltage detection terminal is located at a
distance L2 measured in the longitudinal direction from a
longitudinal end proximate thereto of the resistive body; a current
detecting substrate on which a control circuit is mounted, the
substrate having a voltage detecting portion electrically connected
to the pair of voltage detection terminals for detection of a
voltage across the longitudinal ends of the resistive body; a first
temperature sensor for measuring a temperature of one of the
electrodes of the shunt resistor the first temperature sensor being
located at a distance L1 measured in the longitudinal direction
from a longitudinal end proximate thereto of the resistive body,
wherein the distance L1 is set greater than the distance L2; and a
second temperature sensor for measuring a temperature of the
resistive body.
2. The shunt resistor mount structure according to claim 1, wherein
the first and second temperature sensors are mounted on the
substrate.
3. The shunt resistor mount structure according to claim 1, further
comprising a third temperature sensor for measuring temperatures of
the other of the electrodes of the shunt resistor.
4. The shunt resistor mount structure according to claim 3, wherein
the third temperature sensor is located at a distance L3 measured
in the longitudinal direction from a longitudinal end proximate
thereto of the resistive body, wherein the distance L3 is set
greater than the distance L2.
Description
This application is a 371 application of PCT/JP2019/018361 having
an international filing date of May 8, 2019, which claims priority
to JP2018-095426 filed May 17, 2018, the entire content of each of
which is incorporated herein by reference.
TECHNICAL FIELD
The present invention relates to a shunt resistor mount structure
(a current detection circuit using a shunt resistor).
BACKGROUND ART
A shunt resistor composed of a resistive body and low-resistance
electrodes provided on both ends thereof is known.
For example, in Patent Literature 1, a semiconductor element for
monitoring electric current is provided on a resistive body. The
semiconductor element is disposed on, and in thermal connection
with, a flat surface of a resistive element and/or power connecting
portions. In this way, it is said to be possible to provide, at low
cost, a current measuring device capable of monitoring electric
current accurately in a short time in a power supply system having
a plurality of loads.
CITATION LIST
Patent Literature
Patent Literature 1: JP 2003-270274 A
SUMMARY OF INVENTION
Technical Problem
For example, as illustrated in a perspective view of FIG. 6, a
shunt resistor 101 is conventionally composed of two kinds of
material: a resistive material forming a resistive body 103, and an
electrode material forming electrodes 105a, 105b. Variations in
resistance value temperature characteristics of the shunt resistor
101 are caused based on the characteristics of the two kinds of
material. One is the resistive material, and the other is an
electrically conductive material (conventionally, copper) between
shunt voltage detection signal terminals and junctions between the
resistive material and the electrode terminals. In FIG. 6, the
region of the shunt resistor 101 that has high temperature during
energization, i.e., the region of the resistive body 103, which is
a heating body, is indicated by hatching. As will be seen from FIG.
6, temperature differences are caused between the electrodes 105a,
105b and the resistive body 103 at the time of energization,
wherein the temperatures of the boundary regions are particularly
high.
The two kinds of material have different electrical
conductivity-temperature characteristics, and the shunt resistance
value temperature characteristics are determined by allocation
amounts determined by the structure of the shunt resistor and
affecting the shunt resistance value.
FIG. 7 illustrates an example of temperature changes in resistance
value determined using the shunt resistor 101.
The shunt resistance value temperature characteristics are
determined by the allocation amounts determined by the structure of
the shunt resistor 101 and affecting the shunt resistance value.
The horizontal axis shows temperature, and the vertical axis shows
the rate of change in resistivity as a percent.
Referring to FIG. 7, condition 1 is where manganin temperature is
equal to copper temperature; condition 2 is where manganin
temperature is equal to copper temperature +15.degree. C.;
condition 3 is where manganin temperature is equal to copper
temperature +25.degree. C.; and condition 3 is where manganin
temperature is equal to copper temperature +35.degree. C. In FIG.
7, the solid line (condition 1) indicates an example in which the
shunt resistor 101 not being energized was put into a
constant-temperature bath and resistance value measurement was
performed while varying the temperature. From FIG. 7, data for
condition 1 is obtained.
However, in this case, no consideration is given to the influence
of a temperature difference that is caused between a manganin
portion and a copper portion in an actual energization state, as
described with reference to FIG. 6. Thus, there has been the
problem that only using the temperature of one member does not
constitute an integral temperature compensation process for
high-accuracy current detection.
One aim of the present invention is to provide, in a high-accuracy
current detector based on TCR compensation of shunt resistance in a
current detection circuit using a shunt resistor, a temperature
compensation scheme more accurate than a conventional scheme.
Another aim of the present invention is to enable detection of an
anomaly due to, e.g., defective fastening of a shunt-mounting
screw, before an overheat protection-activating temperature is
reached, thus making it possible to detect an anomaly without
increasing the energization current.
Solution to Problem
According to an aspect of the present invention, there is provided
a shunt resistor mount structure including: a shunt resistor having
a pair of electrodes and a resistive body; a current detecting
substrate on which a control circuit is mounted, the substrate
having a voltage detecting portion to which a pair of voltage
detection terminals of the shunt resistor are connected; and a
temperature sensor for measuring a temperature of the
electrodes.
Preferably, the temperature sensor may be mounted on the substrate.
Mounting on the substrate facilitates temperature correction and
the like.
Preferably, the temperature sensor may include a first temperature
sensor for measuring a temperature of the resistive body.
With the first temperature sensor, it is possible to accurately
measure the temperature of the resistive body, which is a heating
body.
The temperature sensor may include a second temperature sensor and
a third temperature sensor for measuring temperatures of the pair
of electrodes.
With the electrode temperatures sensed by the second and third
temperature sensors and the resistive body temperature sensed by
the first temperature sensor, it is possible to improve temperature
compensation of a shunt resistance value.
Preferably, the second and third temperature sensors may be
provided in positions spaced apart more from the resistive body
than the voltage detection terminals.
By spacing a little away from a joint portion of the resistive
body, which is a heating body, the influence of heating of the
resistive body can be suppressed.
The description includes the contents disclosed in JP Patent
Application No. 2018-095426 based on which the present application
claims priority.
Advantageous Effects of Invention
According to the present invention, it is possible to achieve
high-accuracy current detection for temperature compensation of
shunt resistance value.
According to the present invention, it is also possible to provide
a shunt current detector mount structure which is highly safe,
accurate, and reliable.
BRIEF DESCRIPTION OF DRAWINGS
FIG. 1 is a perspective view illustrating a configuration example
of a current detection device using a shunt resistor according an
embodiment of the present invention.
FIG. 2 is a perspective view illustrating a configuration example
of a shunt resistor mount structure in which a current detector
substrate with a control IC mounted thereon is mounted on the
current detection device using a shunt resistor of FIG. 1.
FIG. 3 illustrates an enlarged view of FIG. 2 in the vicinity of a
first temperature sensor.
FIG. 4 is a perspective view illustrating a configuration in which
a case is attached to cover the substrate in the mount structure
illustrated in FIG. 2.
FIG. 5 is a functional block diagram illustrating a configuration
example of a temperature compensation circuit for the shunt
resistor.
FIG. 6 is a perspective view illustrating a configuration example
of a conventional shunt resistor.
FIG. 7 illustrates an example of resistance value temperature
changes determined using the shunt resistor illustrated in FIG.
6.
DESCRIPTION OF EMBODIMENTS
In the following, a shunt resistor mount structure (a current
detection circuit using a shunt resistor) according to an
embodiment of the present invention will be described in detail
with reference to the drawings.
As used herein, the direction in which the electrode-resistive
body-electrode of a resistor is arranged is referred to as the
length direction, and a direction intersecting the length direction
is referred to as the width direction.
First Embodiment
First, a current detection device 1 using a shunt resistor
according to a first embodiment of the present invention is
described. FIG. 1 is a perspective view illustrating a
configuration example of the current detection device 1 using a
shunt resistor according to the present embodiment. The current
detection device 1 using a shunt resistor illustrated in FIG. 1 is
provided with: two electrodes 5a (a first electrode), 5b (a second
electrode); a resistive body 3 disposed between the electrodes 5a,
5b; and voltage detection terminals 17. A portion composed of the
resistive body 3 and the electrodes 5a, 5b may also be referred to
as an electrically conductive body. The electrodes 5a, 5b may be
referred to as electrode terminals. Each of the electrodes 5a, 5b
is provided with a main electrode portion (the main electrode
portion being defined as a portion of 5a, 5b excluding 5c, 5d) on
the end side, and a narrow electrode portion 5c, 5d on the
resistive body 3 side which is narrower in width than the main
electrode portion by 2W.sub.2. The resistive body 3 is disposed
between the narrow electrode portions 5c, 5d. The narrow electrode
portions 5c, 5d each have a dimension W.sub.1 in the length
direction. The dimension W.sub.1 is on the order of 1 to 3 mm, for
example. In FIG. 1, sign 15 indicates bolt holes.
Both the electrode material and the resistive material may be
obtained by cutting an elongated material (plate), for example.
In the present example, the voltage detection terminals 17 are
provided, one in each of the main electrode portions in the
vicinity of the narrow electrode portions 5c, 5d.
The voltage detection terminals 17 may be provided in the narrow
electrode portions 5c, 5d. By providing the voltage detection
terminals 17 in the narrow electrode portions 5c, 5d or in the main
electrodes in the vicinity thereof, it is possible to reduce the
distance between the voltage detection terminals 17, and to improve
the accuracy of current measurement by four-terminal sensing.
In the structure illustrated in FIG. 1, it is possible to form a
narrow portion or a narrowed width portion having a narrowed width,
by providing recesses 7. The recesses 7 recede inward in the width
direction in partial regions including joint portions 13a, 13b
formed by welding or the like of the resistive body 3 and the
electrode portions 5a, 5b. In this case, the width of the narrow
electrode portions 5c, 5d and the width of the resistive body 3 are
substantially the same. The portion with a narrow width formed by
the recesses 7 is referred to as a narrow portion or a narrowed
width portion.
As the material for the resistive material forming the resistive
body 3, it is possible to use sheet material of Cu--Ni based,
Cu--Mn based, or Ni--Cr based metals, for example. It is also
possible to use manganin (registered trademark) comprising 86%
copper, 12% manganese, and 2% nickel. In the following, an example
is described which includes, but is not limited to, manganin.
FIG. 2 is a perspective view illustrating a configuration example
of a shunt resistor mount structure in which a substrate 21 of a
control IC-equipped current detector is mounted on the current
detection device 1 using a shunt resistor illustrated in FIG.
1.
As illustrated in FIG. 2, the substrate 21 is disposed vertically
on one surface 2a of the current detection device 1 using a shunt
resistor. In the example of FIG. 2, a control IC 51 is mounted on
one surface 21a of the substrate 21. The one surface 2a adjoins a
side surface 21b intersecting the one surface 21a of the substrate
21. In this state, the one surface 21a of the substrate 21 is
formed with terminal accommodating portions 31, 31 for respectively
accommodating the two voltage detection terminals 17, 17, for
example. The terminal accommodating portions 31, 31 have terminal
inserting holes 31a, 31a formed for inserting the two voltage
detection terminals 17, 17. The two voltage detection terminals 17,
17 are electrically connected, in the terminal inserting holes 31a,
31a, to wires or the like, which are not illustrated but formed on
the substrate 21. Accordingly, voltage signals from the two voltage
detection terminals 17, 17 are transmitted to the control IC 51 on
the substrate 21. The control IC 51 is able to determine a current
flowing through the shunt resistor, on the basis of the voltage
signals from the two voltage detection terminals 17, 17.
A connector 41 including a terminal connecting portion 43 for
connection with an external device or the like is formed on the
substrate 21. Thus, it is possible to perform, through the
connector, a process for causing a current value determined by the
control IC 51 to be displayed on the external device, for
example.
In addition, the one surface 21a of the substrate 21 over the one
surface 2a is provided with a first temperature sensor 18a, a
second temperature sensor 18b, and a third temperature sensor 18c.
Sensing signals from the temperature sensors can be read by the
control IC 51, for example.
The first temperature sensor 18a is provided over the electrode 5b
and senses the temperature of the electrode 5b. The first
temperature sensor 18a is preferably provided over the electrode 5b
in the vicinity of the resistive body 3 or in the vicinity of the
recesses 7.
The second temperature sensor 18b is provided over the resistive
body 3 and senses the temperature of the resistive body 3.
The third temperature sensor 18c is provided over the electrode 5a
and senses the temperature of the electrode 5a. The third
temperature sensor 18c is preferably provided over the electrode 5a
in the vicinity of the resistive body 3 or in the vicinity of the
recesses 7.
FIG. 3 is an enlarged view in the vicinity of the first temperature
sensor 18 of FIG. 2. As illustrated in FIG. 2 and FIG. 3, the
position in which the first temperature sensor 18a is disposed is
preferably spaced apart more from the resistive body 3 than the
voltage detection terminal 17 in the length direction. For example,
as illustrated in FIG. 3, when the distance in the length direction
from the position (the center position in the length direction) of
the first temperature sensor 18 to the joint portion 13b is L1, and
the distance in the length direction from the position (center
position) of the voltage detection terminal 17 to the joint portion
13b is L2, it is preferable that L1>L2. L1 is set longer than L2
is because if too close to the joint portion 13b of the resistive
body 3, which is a heating body, the likelihood of being subjected
to the influence of the heating of the resistive body 3 is
greater.
The third temperature sensor 18c also preferably has a positional
relationship similar to that of the first temperature sensor
18a.
The second temperature sensor 18b is preferably provided in the
central position in the length direction of the resistive body 3.
In this way, it is possible to sense the temperature of the
resistive body 3 accurately.
FIG. 4 is a perspective view illustrating a configuration in which
a case 80 is attached to cover the substrate 21 in the mount
structure of FIG. 2. For example, a first case member 81 and a
second case member 83 are provided so as to enclose the substrate
21. The first case member 81 and the second case member 83 may be
configured to be put together into the single case 80 by means of a
known fitting structure. The case 80 is configured such that the
terminal connecting portion 43 of the substrate 21 is disposed
outside the case 80. In this way, it is possible to perform
connection of signal cables or the like from the terminal
connecting portion 43 easily. Further, the electrode portions 5a,
5b are also configured to protrude outside the case 80. In this
way, it is possible to apply a desired voltage across the
electrodes 5a, 5b of the shunt resistor.
As described above, by adopting the structure in which the case
members 81, 83 cover the periphery of the resistive body 3, the
substrate 21 can be protected. Because the substrate 21 and also
the resistive body 3 are accommodated in the case, by performing
temperature compensation with the first to third temperature
sensors 18a to 18c provided for the resistive body 3 and the
electrodes 5a, 5b in the vicinity thereof, it is possible to
perform more accurate temperature compensation taking the influence
of the case into consideration.
(Explanation of Temperature Compensation Circuit)
Next, a temperature compensation circuit using the first to third
temperature sensors 18a to 18c will be described. The temperature
compensation circuit may be mounted in the control Ic 51.
FIG. 5 is a functional block diagram of a configuration example of
a temperature compensation circuit 61 of the shunt resistor 1. As
illustrated in FIG. 5, the temperature compensation circuit 61 is
provided with: an average value calculation circuit 61-1 which
calculates an average value of a measured temperature 1 at the
first temperature sensor 18a, a measured temperature .theta.2 at
the second temperature sensor 18b, and a measured temperature
.theta.3 at the third temperature sensor 18c; a temperature change
calculation unit 61-2 which calculates a temperature change
(temperature increase) .DELTA..theta. of the resistive body 3 of
manganin or the like, on the basis of the measured temperature
.theta.2 and .theta.pin which is the output of the average value
calculation circuit 61-1; a resistance value calculation unit
(including a resistance value table) 61-3 which determines a
resistance value on the basis of .DELTA..theta. and .theta.pin; a
current calculation unit 61-4 which determines a current detected
from the output of a processing unit 61-5 and the resistance value,
the processing unit 61-5 determining the gain and bias of the shunt
resistor 1; and a current signal output calculation unit 61-6 which
determines a current signal output on the basis of the determined
current I.
As described above, by using the temperature compensation circuit
in which the first to third temperature sensors 18a to 18c are
used, it is possible to achieve highly accurate temperature
compensation.
In the configuration described above, in a high-accuracy current
detection device using a shunt resistor, temperature detection
points for compensating the resistance value temperature
characteristics are provided for the resistive element portion of
manganin or the like and also for the copper portions near the
shunt voltage output signals. In this way, it is possible to
measure the temperatures of the resistive body and the electrodes
more accurately, and, therefore, to achieve more highly accurate
temperature compensation.
As described above, the shunt resistor mount structure of the
present embodiment makes it possible to perform high-accuracy
current detection by taking into consideration, for temperature
compensation of the shunt resistance value, the temperature
difference, caused at the time of energization, between the
resistive body of manganin or the like and the electrodes of copper
or the like.
Also, with respect to an abnormal temperature increase in the case
of a shunt-mounting screw fastening failure, an anomaly can be
detected at or below an overheat protection level at a shunt
absolute value temperature, making it possible to provide a shunt
current detector which is highly safe, accurate, and reliable.
In the foregoing embodiment, the configurations and the like that
are illustrated are not to be construed as limiting, but may be
modified, as appropriate, as long as the effects of the present
invention are provided. Other modifications may be made, as
appropriate, and implemented without departing from the scope of
the purpose of the present invention.
The respective constituent elements of the present invention may be
selectively adopted as desired, and an invention comprising a
selectively adopted configuration is also included in the present
invention.
INDUSTRIAL APPLICABILITY
The present invention may be utilized in a shunt resistor mount
structure.
All publications, patents and patent applications cited in the
present description are incorporated herein by reference in their
entirety.
* * * * *